In recent years, a movement has gained traction to replace incandescent light bulbs with lighting fixtures that employ more efficient lighting technologies, as well as to replace relatively efficient fluorescent and high intensity discharge (HID) lighting fixtures with lighting technologies that produce a more pleasing, natural light. One such technology that shows tremendous promise employs light emitting diodes (LEDs) as the light source. Compared with incandescent bulbs, LED-based light fixtures are much more efficient at converting electrical energy into light, are longer lasting, and are also capable of producing light that is very natural. Compared with fluorescent and/or HID lighting, LED-based fixtures are still significantly more efficient and capable of producing light that is much more natural and more capable of accurately rendering colors. As a result, lighting fixtures that employ LED technologies are replacing incandescent, fluorescent, and HID bulbs in residential, commercial, and industrial applications.
The improved efficiency associated with LED-based fixtures is a direct result of the low amount of power that an LED-based fixtures draws in steady-state operation to output a desired amount of light for general illumination. Theoretically, a typical electrical circuit should be able to handle more LED-based fixtures than incandescent, fluorescent, or HID fixtures, given the improved steady-state efficiency of the LED-based fixtures. In practice, however, the nature of the LED-based fixtures has unexpectedly been found to unduly limit the number of LED-based fixtures that one can put on a given electrical circuit.
LED-based fixtures employ power supplies and control circuitry, which are collectively referred to as drivers, to convert an AC supply voltage to a DC supply voltage that is used to power the LEDs and the other electronics of the LED-based fixtures. The power supplies typically include relatively large electrolytic capacitors in their rectification and filter sections. When power is initially supplied to the LED-based fixtures, such as when an individual flips a light switch to turn on the LED-based fixtures, significant inrush currents are initially required to charge the large electrolytic capacitors of the power supplies for all of the LED-based fixtures of the electrical circuit, in addition to the current necessary to drive the LEDs of the LED light source. Once these large electrolytic capacitors are charged, the current draw of the LED-based fixtures is significantly reduced to a steady-state level where the primary current draw is that used to drive the LEDs of the LED light source. In practice, the inrush current levels for the LED-based fixtures are many times greater than the steady-state current levels.
Unfortunately, the inrush currents increase the power ratings for the LED-based fixtures, and as a result, directly limit the number of LED-based fixtures that can be added to a given electrical circuit. While an electrical circuit, as well as the circuit breaker or fuse that protects the electrical circuit, can handle a relatively large number of LED-based fixtures based on the steady-state currents, the elevated inrush currents associated with simultaneously turning the LED-based fixtures on can dramatically limit the number of LED-based fixtures that can be added to the electrical circuit. In many instances, even with a limited number of LED-based fixtures on a given electrical circuit, the elevated inrush currents from simultaneously turning on multiple LED-based fixtures may result in tripped circuit breakers and blown fuses, which are potentially confusing and annoying to property owners and managers.
Limiting the number of LED-based fixtures that can be added to an electrical circuit increases the number of electrical circuits for a given installation, and as such, significantly increases the costs associated with installing LED-based fixtures or prevents the use of LED-based fixtures altogether. Tripping circuit breakers or blowing fuses during normal operation is unacceptable to property owners and managers. Accordingly, there is a need to overcome the limitations imposed on the number of LED-based fixtures that can be added to a typical electrical circuit due to the elevated inrush currents associated with turning on the LED-based fixtures.